Additive manufacturing product and method of producing same

Abstract

An additive manufacturing product that has a chemical composition containing, in mass %, C: 0.030% or more and 0.800% or less, Si: 0.01% or more and 2.50% or less, Mn: 0.10% or more and 8.00% or less, P: 0.100% or less, S: 0.0200% or less, Al: 0.100% or less, N: 0.1000% or less, and O: 0.5000% or less, with the balance being Fe and inevitable impurity. The additive manufacturing product has a steel microstructure where area fraction of pores is 0.50% or less, area fraction of martensite in a region excluding pores is 90% or more, average aspect ratio of prior austenite grains is 1.5 or more, and L HA /L, high-angle grain boundary length L HA divided by grain boundary length L with a misorientation angle of 20° or more and 50° or less, is 2.0 or more.

1 . An additive manufacturing product comprising a chemical composition containing, in mass %,
 C: 0.030% or more and 0.800% or less,   Si: 0.01% or more and 2.50% or less,   Mn: 0.10% or more and 8.00% or less,   P: 0.100% or less,   S: 0.0200% or less,   Al: 0.100% or less,   N: 0.1000% or less, and   O: 0.5000% or less,   with the balance being Fe and inevitable impurity,   and a steel microstructure wherein
 area fraction of pores is 0.50% or less, 
 area fraction of martensite in a region excluding pores is 90% or more, 
 average aspect ratio of prior austenite grains is 1.5 or more, and 
 L HA /L, high-angle grain boundary length L HA  divided by grain boundary length L with a misorientation angle of 20° or more and 50° or less, is 2.0 or more. 
   
     
     
         2 . The additive manufacturing product according to  claim 1 , the chemical composition further containing, in mass %, at least one element selected from the group consisting of:
 Ti: 0.200% or less,   Nb: 0.200% or less,   V: 0.200% or less,   Ta: 0.10% or less,   W: 0.10% or less,   B: 0.0100% or less,   Cr: 1.00% or less,   Mo: 1.00% or less,   Co: 1.000% or less,   Ni: 1.00% or less,   Cu: 1.00% or less,   Sn: 0.200% or less,   Sb: 0.200% or less,   Ca: 0.0100% or less,   Mg: 0.0100% or less,   REM: 0.0100% or less,   Zr: 0.100% or less,   Te: 0.100% or less,   Hf: 0.10% or less, and   Bi: 0.200% or less.   
     
     
         3 . A method of producing the additive manufacturing product according to  claim 1 , the method comprising:
 repeatedly
 laying down metal powder having the chemical composition according to  claim 1  on a stage, and 
 irradiating the metal powder laid down on the stage with a heat source while scanning. 
   
     
     
         4 . The method of producing the additive manufacturing product according to  claim 3 , wherein the heat source is a laser beam or an electron beam. 
     
     
         5 . The method of producing the additive manufacturing product according to  claim 3 , wherein irradiation energy density of the heat source is 60 J/mm 3  or more and 500 J/mm 3  or less. 
     
     
         6 . A method of producing the additive manufacturing product according to  claim 2 , the method comprising:
 repeatedly
 laying down metal powder having the chemical composition according to  claim 2  on a stage, and 
 irradiating the metal powder laid down on the stage with a heat source while scanning. 
   
     
     
         7 . The method of producing the additive manufacturing product according to  claim 6 , wherein the heat source is a laser beam or an electron beam. 
     
     
         8 . The method of producing the additive manufacturing product according to  claim 4 , wherein irradiation energy density of the heat source is 60 J/mm 3  or more and 500 J/mm 3  or less. 
     
     
         9 . The method of producing the additive manufacturing product according to  claim 6 , wherein irradiation energy density of the heat source is 60 J/mm 3  or more and 500 J/mm 3  or less. 
     
     
         10 . The method of producing the additive manufacturing product according to  claim 7 , wherein irradiation energy density of the heat source is 60 J/mm 3  or more and 500 J/mm 3  or less.